1. Field of the Invention
This invention relates to a device for measuring and applying pressure to the skin and underlying tissue of a patient in therapeutic or analgesic quantities. Such a device is useful to therapists and physicians in treating ailments responsive to acupressure or acupuncture or trigger point therapy.
2. Prior Art
Health care practitioners have used a patient's sensitivity to externally applied pressure as a diagnostic tool for at least thirty-five years. The sensitivity to external pressure was indicated by bilateral variation, in pain threshold, is considered symptomatic of certain ailments. Certain neurological and other medical examinations and procedures entail the location and delineation of areas of analgesia or hyposthesia, the former being the absence of pain or touch sensitivity; the latter, reduced pain or touch sensitivity. Also of interest is hyperalgesia, that is, enhanced sensitivity to painful stimuli. Such tests are normally carried out in special examinations for the treatment of neurological disorders as well as in general medical checkups and in diagnosing various diseases.
Cutaneous sensations are transmitted from the skin to various regions of the cerebral cortex. Thus, sensations of touch as well as those of warmth and coolness are perceived and interpreted in particular regions of the somesthetic or bodily sensor area of the parietal lobe. The sensation of pain for each side of the body is conducted to the brain independently. Hence, the sensitivity of a particular area of the body may be compared with a reference area on the opposite side thereof. This comparison, as mentioned above, is useful in diagnosis because as the involvement of the sensory nervous system is unilateral.
In U.S. Pat. No. 4,641,661, Kalurukal describes a device called an algesimeter. The instrument, which is a pain threshold gauge, includes a hand-held pressure sensitive transducer terminating in a pointed probe. When the point of the probe is pressed against the skin, the transducer then yields an electrical signal proportional to the applied pressure, this signal being fed to a resettable digital display. When the pressure applied to the skin reaches a threshold value (at which the patient experiences pain), a switch is actuated by the patient or the health care practitioner to retain the digital indication at that value whereby it may be read by the practitioner and recorded after the instrument is withdrawn from the skin.
Alban, in U.S. Pat. No. 4,505,278, describes a device for algesimetry comprising a gas-type member such as a cylinder for confining a fixed amount of gas and a two-ended member such as a rod. The first end of the rod is pressed against the patient's body to apply gradually increasing pressure, and a second end acting much as a piston in a cylinder, decreases the volume of the fixed amount of gas. Indicia are provided for indicating how much the volume of gas decreases. Alban's device may also be modified to test materials for softness or firmness.
Yet another pain threshold gauge is disclosed in U.S. Pat. No. 2,704,539 to Fisher. Fisher discloses a pen-like instrument having a needle secured to one end of a compressible spring disposed within a tubular casing, the needle going through a bore in the front end of the casing. The other end of the spring is attached to a plunger within whose axial bore is a rotatable shaft having a spiral groove. An indicator pin carried by the plunger extends into this groove. When the needle is pressed against the skin, this acts to axially shift the plunger and thereby rotate the shaft and to cause the indicator pin to advance along a pressure indicating scale. The Fisher device is intended for use in determining paid thresholds and its sharp needle-like point renders it useless for applying precise pressure to the skin and underlying tissue non-invasively.
Kress, in U.S. Pat. No. 4,554,930, describes yet a further device useful for the prevention of pressure induced skin ulceration. The Kress device consists of a pressure sensor for continuously measuring the pressure on a patient's skin at the interface between the skin and a surface exerting pressure on the skin. A monitoring device monitors the pressure exerted on the skin and the elapsed time period during which the skin has been exposed to the measured pressure. An alarm then indicates when the combination of the pressure and the elapsed time is approaching a previously determined level in order to prevent damage to the patient's skin. The Cress device is particularly useful for preventing ulcer formation in patients that are bedridden.
All of the foregoing prior art inventions described devices for detecting levels of pressure which can result in either pain or cell damage. Except for the Alban device, they are all pointed instruments, having a needle-like probe tip which punctures the skin. In addition, all of the foregoing prior art devices, including Alban's, are designed to measure pain thresholds for diagnostic or preventative purposes.
Acupuncture points have been well known in China from earliest times and most of them are held to correspond to specific organs and areas of the body. Acupuncturists work by inserting needles of varying lengths at these points. When particular acupuncture points are stimulated, the corresponding areas being treated respond to the stimulation. Each acupressure point occupies only a very small area, approximately half of a square millimeter on the skin surface. An acupuncture point is highly sensitive and the feeling elicited in response to pressure is quite different from the surrounding tissues. The acupuncturist will, of course, insert his or her needle in such points but non-invasively pressing on the point can be almost as effective. After application of a therapeutic quantity of pressure to a particular acupuncture point, the length of time for which relief lasts will vary from patient to patient from a few minutes to several hours, or even days, but the effectiveness of the point will not diminish through use and the same result will be obtained time and time again.
It is well known that pressure is felt much more intensely by patients at acupuncture points than in adjacent areas to the extent that the pain is felt to be unbearable in the former while being, scarcely felt at all in the latter. It has been noted that Naloxone.RTM. brand of, a morphine antagonist which blocks the action of morphine and of endorphins in the brain, blocks the action of acupressure. Naloxone.RTM. also has the effect of preventing acupressure from relieving pain. Naloxone administered to a patient following acupressure also reverses the pain relief already produced by acupressure. This strongly suggests that acupuncture and acupressure acts by stimulating the production of endorphins. Thus, it has become important to be able to deliver an accurately known pressure to a particular point upon the skin of the body in order to effect relief of pain and other symptoms. The foregoing prior art pain threshold devices simply do not meet the need of the acupuncturist physician or therapist in quantitatively and non-invasively delivering repeatable amounts of pressure to points such as fibromyalgic tender points and myofascial pain trigger points.